Canine Hypoparathyroidism

Canine hypoparathyroidism is a condition that causes a low calcium level and an elevated phosphorous level in dogs. It is most commonly caused by an inappropriate immune system attack on the parathyroid glands. Inadvertent surgical removal may also occur during surgery on the adjacent thyroid gland(s), resulting in the same clinical signs.

In dogs, as in people, the parathyroid glands are located next to the thyroid glands, thus their name. Both are located next to the trachea (windpipe) in the throat.

Canine patients with low calcium levels from any cause usually present with tremors and/or seizures. These are emergency cases,as the seizures must be stopped before permanent damage or even death occurs.

A serum biochemical profile, which would be performed in the process of investigating the cause of any patient’s seizures, will reveal a calcium level substantially below normal. Normal calcium levels for dogs should be between 8.9 and 11.4 mg/dl. Phosphorous levels typically go up in proportion to the decrease in calcium combined with duration of hypocalcemia. Normal phosphorous levels in dogs should be between 2.5 and 6.0 mg/dl.

Treatment is aimed at restoring a normal calcium level in the bloodstream. Oral Vitamin D3 is used, along with oral calcium supplementation. While there are over-the-counter (OTC) forms available, the dosage is much too high for even the largest dog, and compounding of the medication is required. Most patients function well on once-daily dosing.

Overdosing with Vitamin D3 is a significant concern, as excretion of excess calcium in the urine leads to kidney damage, kidney failure and a shortened life. Conversely, if calcium levels fall too low, tremors, seizures and other neurological signs will return. Therefore, regular testing is crucial to ensure proper blood calcium levels are maintained.

Phosphorous levels will be managed by the body in balance with normal calcium levels.

See you tomorrow, Dr. Randolph.